1. Field of the Invention
This invention relates to an improved tamper evident flip top pouring closure for use with a container having a neck with an opening therein. Further, this invention relates to an improved tamper evident flip top pouring closure and container in combination and to a method of construction thereof.
2. Description of the Prior Art
Flip top pouring closures are known where the closure has a central sealing diaphragm. The diaphragm has a loop connected thereto and is scored around a periphery so that the diaphragm can be permanently removed and discarded by manually pulling on the loop (see U.S. Pat. Nos. 3,459,315, 4,356,939, 3,610,484, 4,179,044 and 5,301,849). These closures are usually connected to the container by a skirt that extends outside of the neck of the container. The skirt has a ridge extending along an inner circumference and the neck has a corresponding channel extending along its outer circumference. During installation, when the closure is pushed onto the neck of the container, the ridge slides into the channel to retain the closure on the neck. The flip top is then opened to expose the loop and sealing diaphragm. A consumer pulls the loop to remove the diaphragm and the diaphragm is discarded. Thereafter, the container is opened and closed by opening and closing the flip top. While the sealing diaphragm provides a tamper evident barrier, a disadvantage of these closures is that the entire closure can be pulled off the container so that the ridge slides out of the channel. The contents of the container can then be tampered with without disturbing the sealing diaphragm and the closure can be re-installed on the container by pushing the closure onto the neck until the ridge once again engages the channel. Thus, the tamper evident feature can be circumvented fairly readily.
When the previous closures have a flip top that is connected to the remainder of the closure by a hinge, the closures are made from polypropylene. If polyethylene is used, which is the most common material used for closures, the hinge will fail prematurely as it will break after a fairly small number of openings and closings. The use of polypropylene overcomes the problem with the hinge but the sealing diaphragm can be difficult to remove when the closure is made from polypropylene. This is particularly apparent when the hinge is a live hinge that snaps toward the closed position as it approaches that position. For large caps that have a large diameter, the sealing diaphragm and the loop can be made quite large so that it is easy to tear the diaphragm away from the rest of the closure even when the closure is made of polypropylene. However, for small diameter closures, for example, closures having a diameter of approximately one inch, it is much more difficult to remove the sealing diaphragm when polypropylene is used to make the closure. The loop is quite small and can only be grasped by a thumb and index finger of a user. The force that can be applied to the loop is not very strong. Some consumers have been known to resort to using tools such as a pliers or a kitchen utensil to remove the sealing diaphragm from these types of closures. Some manufacturers have attempted to overcome this problem by manufacturing closures of two different materials, one for the hinge portion and one for the diaphragm portion. It is very difficult to manufacture the closure within one mold from two different materials. It is also much more expensive and time consuming as the mold must be filled to a certain extent with one material and then filled the rest of the way with another material.